Polyetherimide ester elastomers comprised of the reaction products of (a) a low molecular weight diol, (b) a dicarboxylic acid, (c) a high molecular weight poly(oxy alkylene)diamine, and (d) a tricarboxylic acid or its derivative are known and are described in U.S. Pat. Nos. 4,544,734 and 4,556,705 to McCready and in U.S. Pat. No. 4,556,688 to McCready et al. These polyetherimide esters exhibit excellent stress-strain properties, low modulus set, high melting temperatures and/or excellent strength/toughness characteristics as well as superior flexibility, which properties render said polyetherimide esters especially suitable for molding and extrusion applications.
Additionally, polyetherimide ester elastomer resins may be modified to improve certain physical properties and further broaden their scope of application by incorporating therein various additives including fillers and reinforcing agents to enhance toughness and vary the stiffness of the material. Further, such resIns and modified resIns can be blended with other thermoplastic materials to enhance various physical properties and improve processability.
However, many polyetherimide ester elastomer and blends thereof suffer from and their applications are limited by their high flammability. In particular where such resins are to be used for electrical parts, wire coating and building materials, it is most desirable and often required that such materials be resistant to or have low flammability.
Many flame retardant compounds that are utilized in plastics can adversely effect the physical properties of the resin material. Also, it is well recognized that such flame retardant compounds tend to have a high degree of specificity, i.e., they are not universally effective. Rather, they may be inoperable or their effectiveness may vary from poor to excellent depending upon the particular material to be flame retardant.
In selecting suitable flame retardants, it is important to identify flame retardant agents which will impart flame retardancy to the polymer material and still satisfy the performance criteria for the materials. Thus, in addition to achieving flame retardancy, the flame retardant polymeric composition must possess processability, substantially retain to a substantial degree its specified physical properties, exhibit long term aging compatibility and pose no environmental hazards.
With particular reference to polyetherimide ester elastomers it has generally been difficult to adequately render such materials flame retardant without sacrificing, to some degree, their inherent superior physical properties. Specifically, the use of conventional flame retardant additives, in conventional amounts, may generally cause marked decreases in the some of the advantageous physical properties of the elastomers.